The present invention is directed to a method for performing revision surgery to replace a hip prosthesis having a stem portion previously implanted in the intramedullary canal of a femur and to a system for performing such surgery.
As is well known, it is frequently necessary to replace a hip joint prosthesis. This is usually done several years after the original implantation in order to replace disfunctional joints or to obtain the benefits of one of newer design which resulted from advancements in medical technology.
In the course of hip revision surgery, it is necessary to remove the femoral component including its stem from the intramedullary canal of the femur. If cement material was used to fix the stem within the intramedullary canal, it must be removed prior to implantation of the new prosthesis therein. Removal of the cement is accomplished by drilling or reaming. During such drilling or reaming procedure, it is important that the drill or reamer be properly aligned and guided to avoid accidental perforation of the cortex of the femur.
A number of prior art devices have been utilized for aligning drills or reamers in the performance of revision hip surgery. U.S. Pat. No. 4,860,735 relates to a drill alignment guide for osteoplastic surgery in which an alignment rod is supported on a clamp element affixed to the femur. The drill is mounted for movement with an alignment rod which is parallel to and disposed a predetermined distance from a shaft of the drill. As the drill is moved forward, the forward end of the alignment rod moves through an aperture of the clamp element thereby insuring that drilling occurs along a predetermined drilled path extending along the bone axis.
U.S. Pat. No. 4,686,972 relates to a surgical deflector and drilling guide for guiding a drill bit, awl or reamer into a bone. The boring-tool guide assembly comprises a sleeve having a T-shaped nib which can be detachably inserted into a corresponding bracket permanently mounted against a tool having teeth designed to anchor the tool on a boney tissue. The surgeon can insert the tip of a drill bit, awl or reamer into the sleeve of the guide assembly when the teeth are anchored onto the boney tissue to obtain means for guiding the boring tool.
A method of economically removing cement from the femoral canal during revision surgery appeared in the publication "Orthopedics Today", September 1989, pages 18 and 19. Under the procedure described therein, a side cut and end cut reamer positioned in a guide sleeve is utilized to remove the cement.
A catalog entitled "Omniflex.TM. Femoral System Surgical Protocol Press-Fit" copyright 1988 by Osteonics Corp., describes a cement removal system utilizing a tapered axial reamer.
U.S. Pat. No. 4,919,673 is directed to a femoral head prosthesis having a fixing stem with a longitudinal bore utilizing a centering rod extending therethrough and engaged to a barrier at the lower end of the bone cavity.
Following removal of all of the old plastic cement and any cement restricter or plug which may have been used, the cavity remaining in the femur will be substantially larger than is necessary or desirable to accomodate the new femoral hip prosthesis. Accordingly, it is generally accepted procedure to place crushed cancellous bone graft in the enlarged cavity or femoral canal. Prior to positioning the new prosthesis in the femoral canal, the crushed cancellous bone graft is tamped in order to compact it and have it tightly packed in the femoral canal. The stem of the new prosthesis is then placed in the femoral canal with bone cement if the prosthesis is of a type intended for use with bone cement or without bone cement if such prosthesis is of a type intended to be used without such bone cement. If the crushed cancellous bone graft is tightly compacted prior to insertion of the stem of the new prosthesis therein, it may be necessary to enlarge the new cavity in the compacted crushed cancellous bone graft to receive the new prosthesis or use a smaller prosthesis than was intended. As is well known by those skilled in the art, it is necessary that the crushed cancellous bone graft be tightly compacted to provide for strong boney structure around the prosthesis and, if it is not compacted sufficiently tightly prior to introduction of the prosthesis, attempts must be made to further compact it after placement of the new prosthesis in the femoral canal.
The foregoing prior art references are incorporated herein by reference and copies are herewith enclosed.